package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.util.ToStringUtils;

/**
 * A {@link Query} that matches documents containing a subset of terms provided
 * by a {@link FilteredTermEnum} enumeration.
 * <P>
 * <code>MultiTermQuery</code> is not designed to be used by itself. <BR>
 * The reason being that it is not intialized with a {@link FilteredTermEnum}
 * enumeration. A {@link FilteredTermEnum} enumeration needs to be provided.
 * <P>
 * For example, {@link WildcardQuery} and {@link FuzzyQuery} extend
 * <code>MultiTermQuery</code> to provide {@link WildcardTermEnum} and
 * {@link FuzzyTermEnum}, respectively.
 */
public abstract class MultiTermQuery extends Query {
	private Term term;

	/** Constructs a query for terms matching <code>term</code>. */
	public MultiTermQuery(Term term) {
		this.term = term;
	}

	/** Returns the pattern term. */
	public Term getTerm() {
		return term;
	}

	/** Construct the enumeration to be used, expanding the pattern term. */
	protected abstract FilteredTermEnum getEnum(IndexReader reader)
			throws IOException;

	public Query rewrite(IndexReader reader) throws IOException {
		FilteredTermEnum enumerator = getEnum(reader);
		BooleanQuery query = new BooleanQuery(true);
		try {
			do {
				Term t = enumerator.term();
				if (t != null) {
					TermQuery tq = new TermQuery(t); // found a match
					tq.setBoost(getBoost() * enumerator.difference()); // set
																		// the
																		// boost
					query.add(tq, BooleanClause.Occur.SHOULD); // add to query
				}
			} while (enumerator.next());
		} finally {
			enumerator.close();
		}
		return query;
	}

	/** Prints a user-readable version of this query. */
	public String toString(String field) {
		StringBuffer buffer = new StringBuffer();
		if (!term.field().equals(field)) {
			buffer.append(term.field());
			buffer.append(":");
		}
		buffer.append(term.text());
		buffer.append(ToStringUtils.boost(getBoost()));
		return buffer.toString();
	}

	public boolean equals(Object o) {
		if (this == o)
			return true;
		if (!(o instanceof MultiTermQuery))
			return false;

		final MultiTermQuery multiTermQuery = (MultiTermQuery) o;

		if (!term.equals(multiTermQuery.term))
			return false;

		return getBoost() == multiTermQuery.getBoost();
	}

	public int hashCode() {
		return term.hashCode() + Float.floatToRawIntBits(getBoost());
	}
}
